Magnetic couplings



Oct. 18, 1960 R. JAESCHKE 2,955,658

MAGNETIC COUPLINGS Filed Feb. 19, 1958 2 Sheets-Sheet 1 Oct. 18, 1960 R.1.. JAESCHKE MAGNETIC COUPLINGS 2 Sheets-Sheet 2 Arron/v5 x9 INVENTOR.PAL/ L. fire-scams Filed Feb. 19, 1958 Unite MAGNETIC COUPLINGS Ralph L.Jaescliire, Kenosha, Wis., assignor to Eaton Manufacturing Company,Cleveland, Ohio, a corporation of Ohio Filed Feb. 19, 1958, Ser. No.716,166

4 'Claims. (Cl. 192-84) The present invention relates to a magneticcoupling of the torque transmitting type and, more particularly, to amagnetic coupling having dual excitation means, namely, a permanentmagnet excitation means and an electromagnet excitation means, themagnetic coupling being useful in clutches and brakes as well as invarious other applications known to those skilled in the art.

An object of the present invention is to provide a novel magneticcoupling having a permanent magnet excitation means and an electromagnetexcitation means disposed in a series magnetic circuit with respect tothe path of the flux produced by such dual excitation means.

Another object is to provide a magnetic coupling having such dualexcitation means and which is disengageable by cancellation of the fluxof the permanent magnet means by the flux from the electromagnet means.

Another object is to provide a magnetic coupling which is actuatable inone direction by permanent magnets located in a series magnetic circuitand is actuatable in the other direction in response to a cancelling outor bucking of the magnetic flux of the permanent magnets by the flux ofa magnet coil.

Another object of the present invention is to provide an electromagneticcoil in the arrangement set forth in the preceding object where the coilconnections are made in such a manner as to increase the effectivenessof the flux developed by the permanent magnets when the electromagneticcoil has been deenergized.

Another object of the present invention is to provide a magneticcoupling which is actuatable by the combined magnetic fluxes of anannular electromagnet and an annular group of permanent magnetslocatedin a series magnetic circuit relation with the electromagnet.

Another object of the present invention is to provide a new and improvedpermanent magnet excited friction coupling device disengageable byenergizing an electromagnetic. coil arranged to buck the flux of thepermanent magnets having essentially the same series path of minimumlength in which the flux bucking takes place essentially along theentire series path which is free of devious bypass, minor, secondaryand/or auxiliary paths, and low impedance reluctance or interrupterrings for keeper circuits.

Another object of the present invention is the provision of a magneticcoupling substantially in accordance with the preceding objects whereinthe permanent magnets are carried by a rotatable pole structure and thecoil of the electromagnet means is stationary, thereby obviating thenecessity for using slip rings or brushes in connection with theelectromagnet means.

Another object of the present invention is to provide a permanent magnetexcited friction coupling device in which the magnets are of a simpleconfiguration, need not be machined to a special curved shape ormaintained within close tolerances, have a high reluctance todemagnetization, are easily replaced, and/or are capable of beingmagnetized in place.

Another object ofthe present invention is to provide 2,956,658 PatentedOct. 18, 196

a new and improved magnetic coupling of simplified constructionrequiring a minimum number of parts and which is fail-safe due to theprovision of magnets operatively independent of a power supply forpurpose of engagement actuation of the coupling.

The invention further resides in certain novel features of construction,and combinations and arrangements of parts, and further objects andadvantages thereof will be apparent to those skilled in the art to whichit pertains from the following description of the preferred embodimentsthereof described with reference to the accompanying drawing in whichsimilar reference characters represent corresponding parts throughoutthe several views, and in which:

Fig. 1 is a partial axial section of one embodiment of a magneticcoupling in disengaged condition, the view being taken along alongitudinal axis of rotation thereof as indicated by section line 11 ofFig. 2;

Fig. 2 is a partial transverse section taken through the coupling onsection line 2-2 of Fig. 1;

Fig. 3 is a diagram on a smaller scale and corresponding with a portionof Fig. 1, the view showing the coupling in engaged condition andillustrating the flux path of the magnetic circuit;

Fig. 4 is a partial axial view of a modification of the magneticcoupling in disengaged position, the view being taken along alongitudinal axis of rotation thereof as indicated by section line 44 ofFig. 5;

Fig. 5 is a partial transverse section taken through the coupling onsection line 55 of Fig. 4; and

Fig. 6 is a diagram, similar to the diagram of Fig. 3, of a portion ofFig. 4, the view showing the coupling in engaged condition andillustrating the flux path of the magnetic circuit.

Before explaining in detail the preferred embodiments of the presentinvention it is to be understood that the invention is not limited inits application to the details of construction and arrangements of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also, it is to be understood that the phraseology or terminologyemployed herein is for purpose of description and not of limitation, andit is not intended to limit the invention herein claimed beyond therequirements of the prior art.

The magnetic coupling 10 comprises, in general, a pair of axiallyaligned, rotatable shafts 11 and 12, a pole structure 13 connected withthe shaft 11 for rotation therewith, and an armature means 14 rotatablewith the shaft 12 and axially shiftable to engaged and releasedpositions relative to the pole structure. The coupling also comprisesdual excitation means or flux producing means associated with the polestructure 13 and comprising permanent magnet means 1'5 and electromagnetmeans 16.

Referring now to the drawings in greater detail and particularly to Fig.1, the permanent magnet excited friction coupling device 10 comprises adriving shaft 11 and an annular carrier or wheel 17 having a peripheralshoulder 18, the wheel 17 being keyed to the shaft 11 by means of aconventional key 19. A coaxial annular recess 20 in a face 21 of wheel17 reduces the weight thereof. The pole structure 13 comprises twoannular magnetic polepieces 22 and 23 of angular cross section, thepolepiece 22 being rigidly secured to the periphery 24 of wheel 17 inaxial abutment with the shoulder 18. The annulus 22 is comprised of anaxial cylindrical portion 25 and a radial flange-like portion 26.

As best seen in Figure 2, the permanent magnet means 15 consist of aplurality of flat permanent magnets 27 which have a high reluctance todemagnetization and form an annular group or ring about polepiece 22.The permameat magnet 27 are essentially quadrangular, and moreparticularly, square, with the radially inner corners 28 thereofcontiguous with the respective corners 28 of the adjoining permanentmagnets. Each of the magnets 27 is in surface contact with the radialface 29 of the flange-like portion 26 and spaced radially from thecylindrical portion 25 of polepiece 22 a predetermined radial distancefor a reason which will become apparent hereinbelow.

The electromagnet means 16 consists of an electromagnetic coil 30disposed over the cylindrical portion 25 of polepiece 22 and axiallyspaced from the permanent magnets 27. The second annular magneticpolepiece 23 has a radially extending leg 31 and a substantially axiallyextending leg 32, the leg 31 being in flat abutment against the exposedradial faces of the permanent magnets 27. The inner end of radiallyextending leg 31 is beveled at approximately 45 with the innermost endbeing spaced from cylindrical portion 25 of polepiece 22 the samedistance as each of the magnets 27. The 45 bevel serves to reduce thepossibility of and essentially prohibit any magnetic short circuit offlux across the polepieces 22 and 23. Polepiece 23 serves to partiallyenclose the electromagnetic coil 30. Suitable means (not shown) areprovided for supplying energizing current to the coil 30.

A ring-like wear-resistant and nonmagnetic friction lining 33 is seatedagainst two parallel and coplanar annular shoulders 34 and 36 formed inpolepieces 22, 23 and has an outer engageable face coplanar with theends of axially extending leg 32 of polepiece 23 and cylindrical portion25 of the complementary polepiece 22. The corresponding ends of leg 32and cylindrical portion 25, which embrace the friction lining 33therebetween, are fiush with or overhang the corresponding radial endsurface 37 of wheel 17. The corresponding end 38 of shaft 11 may beflush with or terminate axially inwardly of the end surface 37.

Essentially nonmagnetic epoxy resin 39 or the like is used to bond thecoil 30, lining 33, polepiece 23 and permanent magnets 27 together andhold the foregoing elements in assembly with polepiece 22 in theconnected relation shown in the drawings, although any other suitableconnecting medium or means could be used.

The armature means 14 comprises a flat, ring-like mag- V netic armature40 operatively and coaxially disposed oppositely of the polepieces 22,23 and lining 33. Armature 40 is connected to and carried by a disk 42which is splined to a collar 44 and retained thereon for limited axialmovement 'by a snap ring 46 engaged in a suitable annular groove of thecollar. Collar 44 is drivingly connected to an end 48 of driven shaft 12by means of a key '52 therebetween, the ends 33 and 48 of shafts 11 and12, respectively, being essentially coaxial and spaced a relativelyshort distance from each other.

It is to be understood that one of the shafts 11 and 12 can be fixed andthe other shaft rotated for use of the coupling as a brake or,alternatively, the shaft 12 can be the driving shaft and the shaft 11the driven shaft, or vice versa, when the device is used as a torquetransmitting coupling or clutch. The foregoing description is merely byway of describing a preferred embodiment and it is not intended that theinvention be limited thereto.

Referring to Fig. 3, each permanent magnet 27 has suitably locatedmagnet poles and causes magnetic lines of force to travel, preferablycounterclockwise, about coil 30 through polepieces 22, 23 and armature40. However, it is to be understood that the lines of force can also becaused to travel clockwise about the coil 30 in the aforedescribed pathof travel. The coil 30 is so arranged with respect to the pole pieces22, 23 and the armature 40, that it may be energized by connection withits source of energizing current in a manner to generate a flux in adirec ing the coupling. Although the coupling is engageable by the fluxof the permanent magnets 27 alone, by changing the connections of thecoil 30 with its source of energizing current, the flux generated by thecoil can be made to flow in the same direction as that generated by thepermanent magnets, thereby increasing the effective flux tending toengage the coupling. Moreover, since only one path of travel is providedfor the fluxes of both the electromagnet and the permanent magnet means,a considerable savings is realized in weight, materials and cost ofmanufacture not possible in magnetic couplings which require bypasspaths, minor, secondary and/ or auxiliary paths for keeper circuits withthe accompanying necessity for low impedance reluctance or interrupterrings in the keeper circuits.

In addition, due to the placement of the magnets 27 in fiat abutmentwith the leg 31 of polepiece 23 and flangelike portion 26 of polepiece22, the magnets 27 need only be substantially flat and can have anydesirable shape in a plane normal to the rotation axis, although themagnets are shown to be preferably square in Fig. 2. This isadvantageous, since it obviates the costly necessity of machining themagnets which are usually made of a material that is difiicult tomachine.

Also, the advantage of being able to assemble the coupling withouthaving to magnetize the magnets in assembly cannot be overlooked, sincemany magnetic couplings require specially machined and fitted magnetswhich must be assembled with the coupling and then magnetized byapplying electrodes thereto across the polepieces. Moreover, theprovision of a single series circuit for conducting the flux of thepermanent magnets and the electromagnetic coil not only increases theefiiciency and value of the invention but permits the flux of themagnets to be bucked by the flux of the coil along a considerably longerpath than permissible in other constructions.

A second embodiment of the present invention, shown in Figures 4 to 6,comprises a magnetic coupling which is ordinarily engaged, but the fluxof the permanent magnets therein is capable of being substantiallycancelled by the energization of a relatively stationary electromagneticcoil so that the flux generated by the same essentially bucks andcancels out the magnetic lines of force or flux of the permanent magnetsfor disengaging the magnetic coupling.

Essentially, the second embodiment comprises a substantially cylindricalsleeve 60 of magnetic material for forming a magnetic polepiece mountedupon the wheel 17 in a manner described in the first embodiment, whichincludes a shoulder portion 34 for preventing the cylindrical sleeve 60mounted on wheel 17 from being lost oif the end 38 of shaft 11. Frictionlining 33 is seated against an annular radial shoulder 61 in the outerperiphery of cylindrical portion 60. A magnetic polepiece 62, comprisedof an annular, radially extending leg portion 63 and an axiallyextending cylindrical leg portion 64 disposed normal to each other,substantially encloses the outer periphery of the friction lining 33.The radial end face of lining 33 is substantially flush with butslightly overhangs the terminal end of cylindrical portion 64 ofpolepiece 62 and the corresponding end of cylindrical polepiece 60 forbeing spanned and engaged by the magnetic armature 40 which is securedto shaft 12 in a manner hereinbefore described.

In lieu of the large number of quadrangular permanent magnets 27 shownin the first embodiment of the present invention, four substantiallycoplanar arcuate permanent magnets 66 are arranged in a circle aroundthe periphery of the cylindrical sleeve 60 and spaced therefrom. Each ofthe magnets have an arcuate length of about with the adjacent ends ofeach of the arcuate magnets spaced a small distance from each other. Oneof the corresponding radial sides of each of the four magnets is flushwith one of the sides of the radially extending leg portion of thepolepiece 62 away from the lining 33.

' Another annular magnetic polepiece 68, having a configuration somewhatsimilar to the magnetic polepiece 62 is comprised of a radiallyextending leg portion 69 and an axially extending cylindrical legportion 70, each of the polepieces 62 and 68 being substantially coaxialwith the radial leg portions 63 and 69 being substantially parallel, andwith the cylindrical leg portions 64 and 70 lying in axial alignment.Leg portion 70 is slightly longer than leg portion 64 for a reason to beexplained hereinafter. The radially extending leg portion 69 has oneface flush with corresponding radial faces of the permanent magnets 66.The two polepieces 62 and 68, in combination with the permanent magnets66, are held in assembly with cylindrical sleeve 60 and the lining 33 bymeans of appropriate resin 71 similar to that used in the firstembodiment shown in Figures 1 to 3 and, if desired, additionalnonmagnetic fastening means may be used. The radial leg 69 of thepolepiece 68 is counterbored for pro viding a coaxial annular recess 72to aid in preventing a short circuit between the polepiece 68 and theradial sleeve 60. Each of the polepieces 62 and 68 and the cylindricalsleeve 60 are made of a magnetic material which is preferably aferromagnetic material.

A magnetic housing or annulus 73 of U-shaped, or channel-shaped,cross-section opening in an axial direction towards the friction lining33 is rigidly connected to a flat metal ring 75, which is secured to arelatively stationary member 77 by means of cap screws 79, only onebeing shown, or by other appropriate fastening means. The relativelystationary member 77 is formed with a substantially cylindrical opening80 coaxial with the axis of the rotatable shafts 11 and 12.

A t electromagnetic coil 82 is disposed within the channel-snapedhousing 73 and permanently positioned therein by means of a resin 83similar to the epoxy resin used for securing the permanent magnets 27and 66 in place. The channel-shaped annulus is suificiently large toaccommodate the entire annular magnetic coil 82, but has a radialdimension sufficiently small to be interposed between the radiallyextending leg portion 70 of polepiece 68 and over a rear portion of thecylindrical sleeve 60 so that the wheel 17 carrying the permanentmagnets 66 is free to turn relative to stationary coil 82 and itshousing 73. The terminal ends of the axially extending sides of thechannel-shaped housing 73 are spaced axially from the radially extendingportion 69 of the magnetic polepiece 68 a sufficient distance to preventa magnetic short circuit therebetween. However, it is desirable that theaxially extending sides of the channel-shaped housing 73 be radiallyspaced from the cylindrical leg portion 70 of polepiece 68 and thecylindrical sleeve 60 by a very small distance so that air gaps 84 and85 formed between the polepiece 68 and sleeve 60, respectively, aremaintained at a minimum for permitting the flux generated by the magnets66 and the magnetic coil 82 to travel across the air gaps.

For example, referring to Fig. 6, should the poles of the permanentmagnets be arranged in such a manner as to cause the flux to flowcounterclockwise about the magnetic path, then the coil 82 is connectedin such a manner as to generate, when energized, a flux which will buckor travel in a direction counter to the flux of the permanent magnets66, or clockwise about the toroidal flux path. As illustrated in Fig. 6,flux from the permanent magnets 66 will travel, for example, in acounterclockwise direction through polepiece 62, armature 40, magneticsleeve 60, across air gap 85, through channel-shaped annulus 73, acrossthe air gap 84 to polepiece 68 and back to the permanent magnets 66. Asa result, the armature 40, which spans polepieces 60 and 62, isattracted to the polepieces 60 and 62 for engagement therewith.

The flux generated by the electromagnetic coil 82, upon energizationthereof, opposes the fiux of the permanent magnets for bucking andessentially canceling out the flux of the latter for releasing armature40 from polepieces 60 and 62 and disengaging the magnetic coupling.

The permanent magnets 66 preferably have a high permanencecharacteristic, hence the bucking or cancelling action of the coil 82reduces the effective flux to permit the .disengagement of the armature40, without demagnetizing the permanent magnets.

One of the' advantages of the second embodiment of the present inventionis that the number of permanent magnets is considerably reduced forsimplifying the assembly of the magnetic coupling since the large numberof small magnets is eliminated.

Another advantage resides in the elimination of the necessity for sliprings or brushes for conducting electrical energy to a coil mounted on arotating shaft.

While I have shown and described two specific embodiments in accordancewith my invention, it is understood that the same susceptible of manychanges and modifications, as known to a person skilled in the art, andI intend to cover all such changes and modifications as defined in theappended claims.

Having described my invention, what I claim is:

1. A magnetic clutch comprising an annular armature and an annular polestructure, shaft means supporting said armature and pole structure forrelative rotation about a common axis, said armature being shiftablealong said shaft means toward and away from said pole structure forfrictional engagement therewith and release therefrom, said polestructure including first and second pole members, said first polemember including an outer cylindrical portion extending axially towardsaid armature and having an inwardly extending leg portion, said secondpole member including an inner cylindrical portion coaxial with saidouter cylindrical portion and having an outwardly extending leg portion,said inwardly extending leg portion being disposed between saidoutwardly extending leg portion and said armature and with its innermostend spaced from said inner cylindrical portion, a plurality of permanentmagnets disposed between said inwardly extending leg portion and saidoutwardly extending leg portion and forming part of a series magneticflux path including said armature and said pole members, and coil meansdisposed between said pole members and within said series magnetic fluxpath and adapted to be electrically energized to produce a flux in saidseries magnetic flux path, the flux produced by said permanent magnetsin said series magnetic flux path being effective to cause saidfrictional engagement of said armature and the flux produced by saidcoil means being in opposition to the fiux of said permanent magnets andeffective to cause said release of said armature.

2. A magnetic clutch as defined in claim 1 and wherein said coil meansand pole members and said permanent magnets are all bonded together byan epoxy resin.

3. A magnetic clutch as defined in claim 1 and wherein said innermostend of said inwardly extending leg portion is beveled at an angle of 45degrees with respect to said inner cylindrical portion to prevent shortcircuiting of said series magnetic flux path.

4. A magnetic clutch comprising a driving shaft and an axially aligneddriven shaft, an annular armature secured for rotation with one of saidshafts and adapted to be shifted axially therealong, an annularstructure secured for rotation with the other of said shafts and adaptedto be frictionally engaged by said armature, said structure includingspaced concentric first and second polepieces having axially extendingportions and inwardly extending leg portions, the axially extendingportion of said first polepiece extending toward said armature and theaxially extending portion of said second polepiece extending away fromsaid armature, a plurality of permanent magnets disposed between saidleg portions, a cylindrical sleeve concentric with said polepieces andspaced inwardly therefrom, a stationary annular channel shaped memberdisposed between said sleeve and said axially extending portion of saidsecond polepiece, said channel shaped member forming a part of a seriesmagnetic flux circuit with said magnets and polepieces and with saidsleeve and armature, and a stationary electroadapted to generate a fluxin said circuit for shifting said armature into said engagement withsaid srtuctnre and said coil being adapted to create a flux inopposition to the flux of said permanent magnets for releasing saidarmature from said engagement, said polepieces and magnets and saidsleeve all being bonded together by an epoxy resin, said stationary coiland channel shaped member being bonded together by an epoxy resin, andsaid inwardly extending leg portion of said second polepiece having anannular coaxial recess for preventing a 15 21,273

short circuit between said second polepiece and said cylindrical sleeve.

References Cited in the file of this patent UNITED STATES PATENTS2,275,839 Boehne Mar. 10, 1942 2,348,967 Duby May 16, 1944 2,738,449Mason Mar. 13, 1956 2,765,878 Pierce Oct. 9, 1956 2,823,776 Pierce Feb.18, 1958 2,832,918 Pierce Apr. 29, 1958 FOREIGN PATENTS Germany Sept.13, 1955

